Maedi Visna is a chronic disease, caused by a highly contagious virus. It is difficult to diagnose and is fatal. Diagnosis is via a blood test.
It can have huge economic impact on a flock through mortality, reduced lamb growth, increased culling, increased arthritis and infertility.
Affected lambs can have poor growth rates and increased mortality from reduced colostrum intake. Clinical signs in sheep will not usually show until they are adults, due to long viral incubation, however once signs develop the condition is invariably fatal. Signs include wasting, pneumonia, mastitis, arthritis and progressive paralysis.
The virus is transmitted through milk, colostrum, faeces and respiratory secretions. This means both lambs and adult sheep can be affected by the disease.